Molecular cloning, expression and characterization of the human serine/threonine kinase Akt-3
Molecular cloning, expression and characterization of the human serine/threonine kinase Akt-3
复制标题
DOI：
10.1046/j.1432-1327.1999.00774.x
复制
发表时间：
1999-10-01
期刊：
影响因子：
--
通讯作者：
Richardson, A
中科院分区：
文献类型：
--
作者：
Masure, S;Haefner, B;Richardson, A
Akt（也称为 PKB 或 RAC-PK）是一种细胞内丝氨酸/苏氨酸激酶，参与调节细胞存活。尽管这使其成为发现治疗人类癌症药物的有希望的目标，但一个复杂的因素可能是 Akt 在胰岛素信号传导中所发挥的作用。先前已描述了两种人类同工型 Akt-1 和 Akt-2，并且已在大鼠中鉴定出第三种同工型（此处称为 Akt-3，但也称为 RAC-PK-gamma 或 PKB-gamma）。我们描述了相应的人类 Akt-3 同工型的鉴定。编码人类 Akt-3 的基因定位于染色体 1q43-44。预测的蛋白质序列与人 Akt-1 83% 相同，与人 Akt-2 78% 相同，并且包含 pleckstrin 同源结构域和激酶结构域。与已发表的大鼠 Akt-3 亚型相反，人和小鼠 Akt-3 还具有 C 末端“尾巴”，其中包含磷酸化位点 (Ser472)，据信该位点参与 Akt 激酶的激活。除了 Ser472 的磷酸化之外，Thr305 的磷酸化似乎也有助于 Akt-3 的激活，因为这两个残基突变为天冬氨酸会增加 Akt-3 的催化活性，而突变为丙氨酸则会抑制激活。 Akt-3 活性可被广谱激酶抑制剂 staurosporine 和 PKC 抑制剂 Ro 31-8220 抑制，但不会被其他测试的 PKC 或 PKA 抑制剂抑制。尽管 Akt-3 广泛表达，但它在肝脏或骨骼肌中的表达并不高，这表明其主要功能可能不是调节胰岛素信号传导。这些观察结果表明，Akt-3 是发现不干扰胰岛素信号传导的新型化疗药物的有希望的靶标。
Akt (also known as PKB or RAC-PK) is an intracellular serine/threonine kinase involved in regulating cell survival. Although this makes it a promising target for,the discovery of drugs to treat human cancer, a complicating factor may be the role played by Akt in insulin, signalling. Two human isoforms, Akt-1 and Akt-2, have been described previously and a third isoform has been-identified in rats (here termed Akt-3, but also called RAC-PK-gamma or PKB-gamma). We describe the identification of the corresponding human isoform of Akt-3. The gene encoding human Akt-3 was localized to chromosome 1q43-44. The predicted protein sequence is 83% identical to human Akt-1 and 78% identical to human Akt-2, and contains a pleckstrin homology domain and a kinase domain. In contrast to the published rat Akt-3 isoform, human and mouse Akt-3 also possess a C-terminal 'tail' that contains a phosphorylation site (Ser472) thought to be involved in the activation of Akt kinases. In addition to phosphorylation of Ser472, phosphorylation of Thr305 also appears to contribute to the activation of Akt-3 because mutation of both these residues to aspartate increased the catalytic activity of Akt-3, whereas mutation to alanine inhibited activation. Akt-3 activity could be inhibited by:the broad spectrum kinase inhibitor staurosporine and by the PKC inhibitor Ro 31-8220, but not by other PKC or PKA inhibitors tested. Although Akt-3 is expressed widely, it is not highly expressed in liver or skeletal muscle, suggesting that its principle function may not be in regulating insulin signalling. These observations suggest that Akt-3 is a promising target for the discovery of novel chemotherapeutic agents which db not interfere with insulin signalling.